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The thermo e.m.f. of a thermo- couple is...

The thermo e.m.f. of a thermo- couple is `25 muV//^@C` at room temperature. A galvanometer of 40 ohm resistance, capable of detecting current as low as `10^(-5)`A, is connected with the thermo couple. The smallest temperature difference that can be detected by this system is

A

`16^(@)C`

B

`12^(@)C`

C

`8^(@)C`

D

`20^(@)C`

Text Solution

Verified by Experts

The correct Answer is:
A
Thermo-emf of thermocouple is `=25 mu V//^(@)C`
`:.` After connecting the thermocouple with the galvanometer, thermo-emf
`E=25 muV//^(@)Cxx(theta^(@)C)impliesE=250xx10^(-6)V`
Potential drop developed across the galvanometer `=iR=10^(-5)xx40=4xx10^(-4)` volt
`:. 4xx10^(-4)=250xx10^(-6)`
`theta=4/25xx10^(2)=16^(@)C`
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